nucleus-substrate-sdk 0.1.0

Demand-side SDK for the Nucleus substrate. Async HTTP `Client` over the hub plus a single `verify_receipt_fully` entry that walks all four projections (Identity, Capability, Flow, Economic) of a Receipt. Composes substrate-core + identity-projection + flow-projection + mechanism-vcg.
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# nucleus-substrate-sdk

[![Crates.io](https://img.shields.io/crates/v/nucleus-substrate-sdk.svg)](https://crates.io/crates/nucleus-substrate-sdk)
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**Demand-side SDK** for the Nucleus substrate. Composes:

- [`nucleus-substrate-core`](https://crates.io/crates/nucleus-substrate-core) — Session, Receipt, Projection
- [`nucleus-identity-projection`](https://crates.io/crates/nucleus-identity-projection) — JWT-SVID lifter
- [`nucleus-flow-projection`](https://crates.io/crates/nucleus-flow-projection) — Denning-lattice lifter
- [`nucleus-mechanism-vcg`](https://crates.io/crates/nucleus-mechanism-vcg) — Pigouvian-VCG lifter

Two top-level affordances:

- [`Client`] — async HTTP wrapper over the hub's REST surface
- [`verify_receipt_fully`] — composite offline verifier that walks
  every projection in a Receipt

## Quick example

```rust,no_run
use nucleus_substrate_sdk::{Client, verify_receipt_fully};

# async fn ex() -> anyhow::Result<()> {
let client = Client::new("https://nucleus-auction-hub.fly.dev")?;
let receipt = client.fetch_receipt("auction-id").await?;
let jwks    = client.jwks().await?;
let report  = verify_receipt_fully(&receipt, &jwks)?;
println!("✓ verified {} projections", report.projection_kinds.len());
# Ok(()) }
```

## The composite verifier

Pattern lifted from `mc_attestation_verifier`'s `And`/`Or` chain.
`verify_receipt_fully` does:

1. Receipt::verify against issuer's Ed25519 verifying key pulled
   from JWKS by matching `kid`.
2. For each projection in the receipt:
   - `Identity` → `verify_identity_projection`
   - `Flow` → `verify_flow_projection_shape`
   - `Economic` → `verify_economic_projection_shape`
   - `Capability` → skipped in v0.1 (no lifter shipped)

Any failure → `SubstrateVerifyError`.

## Categorical foundation

The composite verifier's correctness is certified in Lean 4 —
see [`receipt_factors_through_projections`][lean-theorem] in
`formal/Nucleus/Substrate/Colimit.lean`. The Receipt is the cocone
vertex of the projection-functor wedge; AND-composition of per-leg
verifiers is the unique universal map.

## License

Dual-licensed under MIT OR Apache-2.0.

[`Client`]: https://docs.rs/nucleus-substrate-sdk/latest/nucleus_substrate_sdk/struct.Client.html
[`verify_receipt_fully`]: https://docs.rs/nucleus-substrate-sdk/latest/nucleus_substrate_sdk/fn.verify_receipt_fully.html
[lean-theorem]: https://github.com/coproduct-private/spiffy/blob/main/formal/Nucleus/Substrate/Colimit.lean